I wonder what op really wants to be told or hear. Is it the way you want to live your life without electricity? I mean do the needful as to what other people do when electricity is gone. As for trading or signing into internet even for trading, look for means to power your gadgets otherwise you wait till electricity is restored.
OP better not to overthink things, yes it might happen and I think the answer is more obvious than the moon.
If we don't have electricity, we can't trade, of course we can't use our desktop and we can use our phones but in very limited time. And I think you'll not die when you didn't trade in a couple of days.
It's more to have an answer for friends who are interested in investing but have these concerns as well.
I was wondering if there are more efforts in minting bitcoins into physical coins, maybe that might be a solution.